staging: mt7621-pci: replace spaces with tabs in comment

To properly follow kernel style replace spaces with tabs in comment
where link status bits are explained.
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>